java.text
Class NumberFormat

NumberFormat is the abstract base class for all number
formats. This class provides the interface for formatting and parsing
numbers. NumberFormat also provides methods for determining
which locales have number formats, and what their names are.

NumberFormat helps you to format and parse numbers for any locale.
Your code can be completely independent of the locale conventions for
decimal points, thousands-separators, or even the particular decimal
digits used, or whether the number format is even decimal.

To format a number for the current Locale, use one of the factory
class methods:

myString = NumberFormat.getInstance().format(myNumber);

If you are formatting multiple numbers, it is
more efficient to get the format and use it multiple times so that
the system doesn't have to fetch the information about the local
language and country conventions multiple times.

To format a number for a different Locale, specify it in the
call to getInstance.

NumberFormat nf = NumberFormat.getInstance(Locale.FRENCH);

You can also use a NumberFormat to parse numbers:

myNumber = nf.parse(myString);

Use getInstance or getNumberInstance to get the
normal number format. Use getCurrencyInstance to get the
currency number format. And use getPercentInstance to get a
format for displaying percentages. With this format, a fraction like
0.53 is displayed as 53%.

You can also control the display of numbers with such methods as
setMinimumFractionDigits.
If you want even more control over the format or parsing,
or want to give your users more control,
you can try casting the NumberFormat you get from the factory methods
to a DecimalNumberFormat. This will work for the vast majority
of locales; just remember to put it in a try block in case you
encounter an unusual one.

NumberFormat and DecimalFormat are designed such that some controls
work for formatting and others work for parsing. The following is
the detailed description for each these control methods,

setParseIntegerOnly : only affects parsing, e.g.
if true, "3456.78" -> 3456 (and leaves the parse position just after index 6)
if false, "3456.78" -> 3456.78 (and leaves the parse position just after index 8)
This is independent of formatting. If you want to not show a decimal point
where there might be no digits after the decimal point, use
setDecimalSeparatorAlwaysShown.

setDecimalSeparatorAlwaysShown : only affects formatting, and only where
there might be no digits after the decimal point, such as with a pattern
like "#,##0.##", e.g.,
if true, 3456.00 -> "3,456."
if false, 3456.00 -> "3456"
This is independent of parsing. If you want parsing to stop at the decimal
point, use setParseIntegerOnly.

You can also use forms of the parse and format
methods with ParsePosition and FieldPosition to
allow you to:

progressively parse through pieces of a string

align the decimal point and other areas

For example, you can align numbers in two ways:

If you are using a monospaced font with spacing for alignment,
you can pass the FieldPosition in your format call, with
field = INTEGER_FIELD. On output,
getEndIndex will be set to the offset between the
last character of the integer and the decimal. Add
(desiredSpaceCount - getEndIndex) spaces at the front of the string.

If you are using proportional fonts,
instead of padding with spaces, measure the width
of the string in pixels from the start to getEndIndex.
Then move the pen by
(desiredPixelWidth - widthToAlignmentPoint) before drawing the text.
It also works where there is no decimal, but possibly additional
characters at the end, e.g., with parentheses in negative
numbers: "(12)" for -12.

Before calling, set status.index to the offset you want to start
parsing at in the source.
After calling, status.index is the end of the text you parsed.
If error occurs, index is unchanged.

When parsing, leading whitespace is discarded
(with successful parse),
while trailing whitespace is left as is.

Example:
Parsing "_12_xy" (where _ represents a space) for a number,
with index == 0 will result in
the number 12, with status.index updated to 3
(just before the second space).
Parsing a second time will result in a ParseException
since "xy" is not a number, and leave index at 3.

Subclasses will typically supply specific parse methods that
return different types of values. Since methods can't overload on
return types, these will typically be named "parse", while this
polymorphic method will always be called parseObject.
Any parse method that does not take a status should
throw ParseException when no text in the required format is at
the start position.

parse

Returns a Long if possible (e.g., within the range [Long.MIN_VALUE,
Long.MAX_VALUE] and with no decimals), otherwise a Double.
If IntegerOnly is set, will stop at a decimal
point (or equivalent; e.g., for rational numbers "1 2/3", will stop
after the 1).
Does not throw an exception; if no object can be parsed, index is
unchanged!

isParseIntegerOnly

public boolean isParseIntegerOnly()

Returns true if this format will parse numbers as integers only.
For example in the English locale, with ParseIntegerOnly true, the
string "1234." would be parsed as the integer value 1234 and parsing
would stop at the "." character. Of course, the exact format accepted
by the parse operation is locale dependant and determined by sub-classes
of NumberFormat.

setParseIntegerOnly

getInstance

Returns the default number format for the current default locale.
The default format is one of the styles provided by the other
factory methods: getNumberInstance, getCurrencyInstance or getPercentInstance.
Exactly which one is locale dependant.

getInstance

Returns the default number format for the specified locale.
The default format is one of the styles provided by the other
factory methods: getNumberInstance, getCurrencyInstance or getPercentInstance.
Exactly which one is locale dependant.

clone

CloneNotSupportedException - if the object's class does not
support the Cloneable interface. Subclasses
that override the clone method can also
throw this exception to indicate that an instance cannot
be cloned.

isGroupingUsed

public boolean isGroupingUsed()

Returns true if grouping is used in this format. For example, in the
English locale, with grouping on, the number 1234567 might be formatted
as "1,234,567". The grouping separator as well as the size of each group
is locale dependant and is determined by sub-classes of NumberFormat.

getMaximumIntegerDigits

setMaximumIntegerDigits

public void setMaximumIntegerDigits(int newValue)

Sets the maximum number of digits allowed in the integer portion of a
number. maximumIntegerDigits must be >= minimumIntegerDigits. If the
new value for maximumIntegerDigits is less than the current value
of minimumIntegerDigits, then minimumIntegerDigits will also be set to
the new value.

Parameters:

newValue - the maximum number of integer digits to be shown; if
less than zero, then zero is used. The concrete subclass may enforce an
upper limit to this value appropriate to the numeric type being formatted.

getMinimumIntegerDigits

setMinimumIntegerDigits

public void setMinimumIntegerDigits(int newValue)

Sets the minimum number of digits allowed in the integer portion of a
number. minimumIntegerDigits must be <= maximumIntegerDigits. If the
new value for minimumIntegerDigits exceeds the current value
of maximumIntegerDigits, then maximumIntegerDigits will also be set to
the new value

Parameters:

newValue - the minimum number of integer digits to be shown; if
less than zero, then zero is used. The concrete subclass may enforce an
upper limit to this value appropriate to the numeric type being formatted.

getMaximumFractionDigits

setMaximumFractionDigits

public void setMaximumFractionDigits(int newValue)

Sets the maximum number of digits allowed in the fraction portion of a
number. maximumFractionDigits must be >= minimumFractionDigits. If the
new value for maximumFractionDigits is less than the current value
of minimumFractionDigits, then minimumFractionDigits will also be set to
the new value.

Parameters:

newValue - the maximum number of fraction digits to be shown; if
less than zero, then zero is used. The concrete subclass may enforce an
upper limit to this value appropriate to the numeric type being formatted.

getMinimumFractionDigits

setMinimumFractionDigits

public void setMinimumFractionDigits(int newValue)

Sets the minimum number of digits allowed in the fraction portion of a
number. minimumFractionDigits must be <= maximumFractionDigits. If the
new value for minimumFractionDigits exceeds the current value
of maximumFractionDigits, then maximumIntegerDigits will also be set to
the new value

Parameters:

newValue - the minimum number of fraction digits to be shown; if
less than zero, then zero is used. The concrete subclass may enforce an
upper limit to this value appropriate to the numeric type being formatted.

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